Add GetAbsoluteMediaUrl method to UrlHelper for the Open Graph starter kit lesson

src/Umbraco.Web/UrlHelperRenderExtensions.cs

@@ -343,5 +343,24 @@ namespace Umbraco.Web
         {
             return url.SurfaceAction(action, typeof (T), additionalRouteVals);
         }
+
+        /// <summary>
+        /// Generates a Absolute Media Item URL based on the current context
+        /// </summary>
+        /// <param name="urlHelper"></param>
+        /// <param name="mediaItem"></param>
+        /// <returns></returns>
+        public static string GetAbsoluteMediaUrl(this UrlHelper urlHelper, IPublishedContent mediaItem)
+        {
+            if (urlHelper == null) throw new ArgumentNullException("urlHelper");
+            if (mediaItem == null) throw new ArgumentNullException("mediaItem");
+
+            if (urlHelper.RequestContext.HttpContext.Request.Url != null)
+            {
+                var requestUrl = urlHelper.RequestContext.HttpContext.Request.Url.GetLeftPart(UriPartial.Authority);
+                return string.Format("{0}{1}", requestUrl, mediaItem.Url);
+            }
+            return null;
+        }
     }
 }